package com.lagou.sqlsession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;
import com.lagou.utils.TokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor{
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1、注册驱动，获取驱动
        Connection connection = configuration.getDataSource().getConnection();

        //2、获取sql语句,转化占位符
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4、设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterClass = getClass(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramterClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

        //5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        //6、封装结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClass(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);

                //使用反射或内省
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        //1、注册驱动，获取驱动
        Connection connection = configuration.getDataSource().getConnection();

        //2、获取sql语句,转化占位符
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3、获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4、设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterClass = getClass(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramterClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

        //5、执行sql
        int result = preparedStatement.executeUpdate();

        return result;
    }

    private Class<?> getClass(String paramterType) throws ClassNotFoundException {
        if (paramterType != null){
            return Class.forName(paramterType);
        }
        return null;
    }

    /**
     * 将#{}转换为？
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        return new BoundSql(parseSql,parameterMappings);
    }
}
